REV. C
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a
AD7823
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2000
2.7 V to 5.5 V, 5 s, 8-Bit
ADC in 8-Lead microSOIC/DIP
FUNCTIONAL BLOCK DIAGRAM
CLOCK
OSC
D
OUT
SCLK
V
REF
AGND
V
DD
V
IN+
V
IN–
CONVST
SERIAL
PORT
CHARGE
REDISTRIBUTION
DAC
CONTROL
LOGIC
AD7823
COMP
V
DD
/3
FEATURES
8-Bit ADC with 4 s Conversion Time
Small Footprint 8-Lead microSOIC Package
Specified Over a –40ⴗC to +125ⴗC Temperature Range
Inherent Track-and-Hold Functionality
Operating Supply Range: 2.7 V to 5.5 V
Specifications at 2.7 V to 5.5 V and 5 V ⴞ 10%
Microcontroller Compatible Serial Interface
Optional Automatic Power-Down
Low Power Operation:
570 W at 10 kSPS Throughput Rate
2.9 mW at 50 kSPS Throughput Rate
Analog Input Range: 0 V to V
REF
Reference Input Range: 0 V to V
DD
“Drop In” Upgrade to 10 Bits Available (AD7810)
APPLICATIONS
Low Power, Hand-Held Portable Applications
Requiring Analog-to-Digital Conversion
with 8-Bit Accuracy, e.g.,
Battery-Powered Test Equipment
Battery-Powered Communications Systems
GENERAL DESCRIPTION
The AD7823 is a high speed, low power, 8-bit A/D converter
that operates from a single 2.7 V to 5.5 V supply. The part con-
tains a 4 µs typ successive approximation A/D converter, inherent
track-and-hold functionality (with a pseudo differential input)
and a high speed serial interface that interfaces to most microcon-
trollers. The AD7823 is fully specified over a temperature range
of –40°C to +125°C.
By using a technique that samples the state of the CONVST
(convert start) signal at the end of a conversion, the AD7823
may be used in an automatic power-down mode. When used in
this mode, the AD7823 powers down automatically at the end
of a conversion and “wakes up” at the start of a new conversion.
This feature significantly reduces the power consumption of the
part at lower throughput rates. The AD7823 can also operate in
a high speed mode where the part is not powered down between
conversions. In this high speed mode of operation, the conver-
sion time of the AD7823 is 4 µs typ. The maximum throughput
rate is dependent on the speed of the serial interface of the
microcontroller.
The part is available in a small, 8-lead 0.3" wide, plastic dual-in-
line package (mini-DIP); in an 8-lead, small outline IC (SOIC);
and in an 8-lead microSOIC package.
PRODUCT HIGHLIGHTS
1. Complete, 8-Bit ADC in 8-Lead Package
The AD7823 is an 8-bit 4 µs typ ADC with inherent track-
and-hold functionality and a high speed serial interface—all
in an 8-lead microSOIC package. V
REF
may be connected to
V
DD
to eliminate the need for an external reference. The result
is a high speed, low power, space saving ADC solution.
2. Low Power, Single Supply Operation
The AD7823 operates from a single 2.7 V to 5.5 V supply and
typically consumes only 9 mW of power. The power dissipa-
tion can be significantly reduced at lower throughput rates by
using the automatic power-down mode, e.g., at a throughput
rate of 10 kSPS the power consumption is only 570 µW.
3. Automatic Power-Down
The automatic power-down mode, whereby the AD7823
“powers down” at the end of a conversion and “wakes up”
before the next conversion, means the AD7823 is ideal for
battery powered applications. See Power vs. Throughput
Rate section.
4. Serial Interface
An easy to use, fast serial interface allows connection to most
popular microprocessors with no external circuitry.
